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Throttle Position Sensor

noosaj

By noosaj
in Ask A GM Technician

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noosaj Enthusiast

noosaj

Posted
Posted

I apologize in advance for asking a stupid question. Where is the throttle position sensor located on the truck? Got a 2003 Chevy Silverado 4.8L V8.

 

Thanks in advance.

 

Jason

noosaj Enthusiast

noosaj

Posted
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Posted

Anyone? The reason I ask this question is this: message center in my truck says "REDUCED ENGINE POWER". Won't go any faster than 20 mph. That puzzled me because I drove it fine the last three days back and forth from/to work/home. Parked it overnight, and this morning I tried to start it. Came on but with a new message as stated above. Wanted to know what was going on, so did some research and discovered that it was most likely throttle related issues. Air filter's good, coolant's good, checked all visible wires under the hood and looks good. Checked fuses and relays - all look good. Not sure what's going on and hope someone here can help me. Most say to send it to a shop and get it diagnosed; however, I'm pretty good with vehicles and I'd like to try and fix it before spending hundreds of dollars on something that I could have fixed.

 

I'm trying to locate the TPS, and am not sure whether it's on the throttle body (the black part attached to the left of it when you're looking in the hood), or directly attached to the accelerator pedal. How do I determine which has gone bad?

longhorn_giant Enthusiast

longhorn_giant

Posted
Posted

I used to have an '02 4.3L V6 and had to replace the TPS. The V6 was still a distributer-powered engine, so I wasn't sure if your setup was the same. It's the black piece on the left side of the throttle body. With the connector plug on it, it is kind of 'T' shaped. When I was working on mine the bolts were torx-bit bolts, and in pretty bad shape. It was easier for me to take the throttle body off to get it off.

 

Sorry I didn't reply earlier, I thought someone else with experience with the V8 in those trucks would have responded.

 

A good way to test it is to take a volt-meter on the hot wire in the connector, then use a screwdriver to turn the sensor piece. You should see the resistance vary. If it's working, you might look at the wiring/connection to the TPS, it was in pretty bad shape on my '02 when I started messing with it.

noosaj Enthusiast

noosaj

Posted
  • Author
Posted

Right, but my engine is not overheating. In fact, I can't find anything wrong with it. I guess I have no choice but to have it towed to a Chevy dealer and have them diagnose the problem.

 

Thanks.

noosaj Enthusiast

noosaj

Posted
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bill190, after further research and looking into my manual, you are exactly right. I have the manual right in front of me. In fact, I do remember several days earlier I had a "LOW COOLANT LEVEL" message appear and that puzzled me. Two days ago, while my truck was sitting outside, not being able to drive it, I checked the coolant level and noticed it was really low, so I added more coolant and got it to the level it needs to be.

 

Now, the question is, how do I get the truck to recognize that there's more coolant and all is good? In other words, how do I "reset" it?

 

Thanks!!

noosaj Enthusiast

noosaj

Posted
  • Author
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Alright, guys. Here's the latest. I've fiddled with the TPS by the throttle body. All wiring looks good. Here's what I did. I unplugged the TPS wiring from the throttle body and ran the engine. It ran a big higher than idle, say around 1500 RPM. Keep in mind, before I unplugged the TPS wiring, I could not give it any gas by pressing the accelerator pedal. After unplugging it for a few minutes, I turned off the engine, and plugged it back in. Started 'er up back again, and now I can control throttle up to 2500 RPM, but still have a "REDUCED ENGINE POWER" message and cannot get full control back.

 

My assumption is the TPS has gone bad. What do you guys think?

noosaj Enthusiast

noosaj

Posted
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Posted

Also, after doing this test, after successfully being able to control throttle up to 2500 RPM, I turned off the engine. Started it back up again, and now I cannot control throttle at all. TPS gone bad?

noosaj Enthusiast

noosaj

Posted
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The TPS is not located on the left of the throttle body. I believe that's the throttle actuator control. I, for the life of me, cannot locate my TPS in my truck. Can anyone tell me please?

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

you are wasting your time,that msg is for an electrical fault and you need to go get it scanned ,it may have to do with the APP sensor,I can't remember ,do not throw parts at it ,you can't get diagnoses over the internet especially electrical!!!

jrmh165 Enthusiast

jrmh165

Posted
Posted
you are wasting your time,that msg is for an electrical fault and you need to go get it scanned ,it may have to do with the APP sensor,I can't remember ,do not throw parts at it ,you can't get diagnoses over the internet especially electrical!!!

 

 

Your throttle position sensor is ran by a computer that on the firewell and it went bad. i had the same problem when i worked in the dealer. sorry for the bad news

  • 2 weeks later...
noosaj Enthusiast

noosaj

Posted
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Posted

Everyone,

 

Thanks for your comments and advice. After some long diagnostics and tinkering, I found that the throttle actuator control went bad. Replaced the *entire* throttle body w/ actuator, since the two cannot be separated, and the truck runs like new and all codes went away.

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